Method and system for deghosting

ABSTRACT

In one embodiment the invention comprises a method for receiving an acoustic wavefield beneath the surface of the water in which at least a portion of an acoustic wavefield is received at a first position, at least a portion of an acoustic wavefield is received at a second position, and at least a portion of an acoustic wavefield is received at a third position. The first position, the second position and the third position are triangularly positioned relative to one another. The first position is not directly above or below the second position or the third position, and the second position is not directly above or below the third position.

This is a division of application Ser. No. 09/728,266 filed Dec. 1, 2000now U.S. Pat. No. 6,477,470

BACKGROUND OF THE INVENTION

Currently in the art of geophysical marine seismic prospecting, a vesseltows very long streamers which have many seismic receivers attached.Often these streamers are miles long. These receivers receive a portionof a scattered acoustic wavefield originated from the sounding of aseismic source. The acoustic wavefield generated by the seismic sourceis scattered by reflections and refractions in the earth. Because thesestreamers are very long, have many receivers, and are towed behind amoving vessel, the coverage in the sail—or in-line direction—is verylarge. However, only a few streamers can be towed behind the vessel atany one time. Therefore, there is relatively very little coverage of thestreamers in the cross-line direction. While there are variousconventional methods to increase the number of streamers a vessel cantow in the cross-line direction, this coverage is still much less thanin the in-line direction.

Because this coverage is very small, very little cross-line processinghas been developed. Instead, development has concentrated on in-lineprocessing. Furthermore, conventional in-line processing simply is notsuitable for cross-line data. Currently, various passes with the vesselare made. During each of these passes, limited cross-line information isgathered. The processors then recreate the information in the cross-linedirection by patching the data together. This is both inaccurate andexpensive.

Furthermore, because this data must be then processed onshore muchlater, conventional methods have not been able to determine the qualityof the in-line or cross-line data received while the vessel is stillnear the acquisition site. This results in a wasted opportunity toaccurately collect data.

Turning now to streamer configurations, further conventional methodsteach using various levels of streamers towed at differentdepths—usually two. These conventional methods teach to tow these cablesdirectly above one another. This is difficult to do. Ocean currents tendto thrust the miles and miles of cables. Despite this fact, conventionalmethods continue to design processing algorithms for streamers toweddirectly above one another.

As a result, there is a long felt need for a method and system fordeghosting seismic data in both the in-line direction and the cross-linedirection, an improved quality control method for data acquisition, andan improved streamer configuration for vertically separated cables.

SUMMARY OF THE INVENTION

In one embodiment of the present invention, a method for processing ascattered acoustic wavefield is provided. The scattered acousticwavefield (230) is received by at least two receivers (201). Thesereceivers (201) are offset (250) and located at approximately the samedepth (205). The method comprises transforming (101) the scatteredacoustic wavefield (230) to the frequency domain (101). The method alsocomprises transforming (105) the scattered acoustic wavefield (230) fromthe frequency domain to the spectral domain. The method also comprisesdeghosting (110) the scattered acoustic wavefield (230) in the spectraldomain. The method further comprises transforming (115) thesubstantially deghosted transformed acoustic wavefield to the space-timedomain.

In an even further embodiment of the present invention, a method forprocessing a scattered acoustic wavefield (230) received by at least afirst set (501) of two receivers (201) and at least a second set (502)of two receivers (201) is provided. The first set (501) of two receivers(201) is offset (250) at substantially a first depth (515) which isvertically offset (520) from at least a second set (502) of tworeceivers (201) offset (250) at substantially a second depth (505). Themethod comprises transforming (401) the scattered acoustic wavefield(230) received at the first depth (515) to the frequency domain. Themethod further comprises transforming (405) the scattered acousticwavefield (230) received at the second depth (505) to the frequencydomain (405). The method further comprises transforming (410) thescattered acoustic wavefield (230) received at the first depth (515)from the frequency domain to the spectral domain. The method furthercomprises transforming (415) the scattered acoustic wavefield (230)received at the second depth (505) from the frequency domain to thespectral domain. The method also comprises generating (420) asubstantially deghosted scattered acoustic wavefield in the spectraldomain. The method further comprises transforming (425) thesubstantially deghosted scattered acoustic wavefield to the space-timedomain.

In an even further embodiment, a method for receiving an acousticwavefield beneath the surface of the water is also provided. In oneembodiment, the method comprises receiving at least a portion of anacoustic wavefield (230) at a first position (701). The method alsocomprises receiving at least a portion of an acoustic wavefield (230) ata second position (702) and receiving at least a portion of an acousticwavefield (230) at a third position (703). The first position (701), thesecond position (702), and the third position (703) are triangularlypositioned (720) relative to one another.

In another embodiment of the present invention, a method of controllingthe quality of seismic data acquisition substantially near theacquisition site is provided. The method comprises generating (901) ascattered acoustic wavefield (230). The method further comprisesreceiving (905) at least a portion of the scattered acoustic wavefield(230). The method further comprises substantially deghosting (910) thescattered acoustic wavefield (230) relatively near the acquisition site.The method further comprises evaluating (915) the quality of thesubstantially deghosted scattered acoustic wavefield.

In a further embodiment, a system for processing a scattered acousticwavefield (230) received by at least two receivers (201) offset (250) atsubstantially the same depth (205) is provided. The system comprisesmeans for transforming (1101) the scattered acoustic wavefield (230) tothe frequency domain. The system further comprises means fortransforming (1101) the scattered acoustic wavefield (230) from thefrequency domain to the spectral domain. The system further comprisesmeans for deghosting (1115) the scattered acoustic wavefield in thespectral domain. The system further comprises means for transforming(1120) the substantially deghosted transformed acoustic wavefield (230)to the space-time domain.

In an even further embodiment, the system comprises a means fortransforming (1201) the scattered acoustic wavefield (230) received atthe first depth (515) to the frequency domain. The system furthercomprises means for transforming (1205) the scattered acoustic wavefield(230) received at the second depth (505) to the frequency domain. Thesystem further comprises means for transforming (1210) the scatteredacoustic wavefield (230) received at the first depth (515) from thefrequency domain to the spectral domain. The system further comprises ameans for transforming (1215) the scattered acoustic wavefield (230)received at the second depth (505) from the frequency domain to thespectral domain. The system further comprises means for generating(1220) a substantially deghosted scattered acoustic wavefield in thespectral domain. The system further comprises means for transforming(1225) the substantially deghosted scattered acoustic wavefield to thespace-time domain.

In still another embodiment of the present invention, a system forreceiving an acoustic wavefield beneath the surface of the water isprovided. The system comprises means for receiving at least a portion ofan acoustic wavefield at a first position (1305). The system furthercomprises means for receiving at least a portion of an acousticwavefield at a second position (1310). The system further comprisesmeans for receiving at least a portion of an acoustic wavefield at athird position (1315). In an even further embodiment, the first position(1315), the second position (1310), and the third position (1315) aretriangularly positioned relative to one another.

In a further embodiment, a system of controlling the quality of seismicdata acquisition substantially near the acquisition site is provided.The system comprises a means for generating (1401) a scattered acousticwavefield (230). The system further comprises a means for receiving(1405) at least a portion of the scattered acoustic wavefield (230). Thesystem further comprises a means for substantially deghosting (1410) thescattered acoustic wavefield (230) relatively near the acquisition site.The system further comprises a means for evaluating (1415) the qualityof the substantially deghosted scattered acoustic wavefield.

In an even further embodiment, an apparatus for processing a scatteredacoustic wavefield (230) received by at least two receivers (201) isprovided. The receivers (201) are offset (250) and located atapproximately the same depth (205). The apparatus comprises a frequencydomain transformer (1501). The apparatus further comprises a spectraldomain transformer (1505). The apparatus further comprises a deghoster(1510). The apparatus further comprise a space-time domain transformer(1515).

In an even further embodiment, an apparatus for processing a scatteredacoustic wavefield (230) received by at least a first set (501) of tworeceivers (201) and a second set (502) of two receivers (201) isprovided. The first set (501) of two receivers (201) is offset (250) atsubstantially a first depth (515) which is vertically offset (520) fromat least a second set (502) of two receivers (201) offset (250) atsubstantially a second depth (505). The apparatus comprises a firstdepth frequency domain transformer (1601). The apparatus also comprisesa second depth (505) frequency domain transformer (1605). The apparatusfurther comprises a first depth (515) spectral domain transformer(1610). The apparatus further comprises a second depth (505) spectraldomain transformer (1615). The apparatus also comprises a space-timedomain transformer (1625).

In an even further embodiment of the present invention, a streamerconfiguration is provided. The streamer configuration comprises a firstseismic streamer (710), a second seismic streamer (740) and a thirdseismic streamer (730). In this configuration the first seismic streamer(710), the second seismic streamer (740), and the third seismic streamer(730) are essentially triangularly positioned relative to one another.Furthermore, the first streamer (710) is not directly above or below thesecond (740) or third (730) streamer. The second streamer (740) is notdirectly above or below the third streamer (730).

In an even further embodiment, an apparatus of controlling the qualityof seismic data acquisition at the acquisition site is provided. Theapparatus comprises a scattered acoustic wavefield (230) generator(1701). The apparatus further comprises a scattered acoustic wavefield(230) receiver (1705). The apparatus further comprises a deghoster(1710). The apparatus also comprises a quality evaluator (1715).

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a block diagram of an example embodiment of a method of thepresent invention.

FIG. 2 is a diagram of various aspects of example embodiments of thepresent invention in the marine environment.

FIG. 3 is a diagram of various aspects of example embodiments of thepresent invention in the marine environment.

FIG. 4 is a block diagram of an example embodiment of a method of thepresent invention.

FIG. 5 is a diagram of various aspects of example embodiments of thepresent invention in the marine environment.

FIG. 6 is a diagram of various aspects of example embodiments of thepresent invention in the marine environment.

FIG. 7 is a diagram of various aspects of example embodiments of amethod, system, and apparatus of the present invention.

FIG. 8 is a diagram of various aspects of example embodiments of amethod, system, and apparatus of the present invention.

FIG. 9 is a block diagram of an example embodiment of a method of thepresent invention.

FIG. 10 is a diagram of various aspects of example embodiments of amethod, system, and apparatus of the present invention in the marineenvironment.

FIG. 11 is a block diagram of an example embodiment of a system of thepresent invention.

FIG. 12 is a block diagram of an example embodiment of a system of thepresent invention.

FIG. 13 is a block diagram of an example embodiment of a system of thepresent invention.

FIG. 14 is a block diagram of an example embodiment of a system of thepresent invention.

FIG. 15 is a block diagram of an example embodiment of an apparatus ofthe present invention.

FIG. 16 is a block diagram of an example embodiment of an apparatus ofthe present invention.

FIG. 17 is a block diagram of an example embodiment of an apparatus ofthe present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE PRESENT INVENTION

In one embodiment of the present invention, a method for processing ascattered acoustic wavefield is provided. As illustrated in FIGS. 1, 2,and 3 in this embodiment, the scattered acoustic wavefield (230) isreceived by at least two receivers (201). These receivers (201) areoffset (250) and located approximately at the same depth (205) asillustrated in FIGS. 2 and 3. Turning to FIG. 1, the method comprisestransforming (101) the scattered acoustic wavefield (230) to thefrequency domain. The method also comprises transforming (105) thescattered acoustic wavefield (230) from the frequency domain to thespectral domain. The method further comprises deghosting (110) thescattered acoustic wavefield (230) in the spectral domain andtransforming (115) the substantially deghosted transformed acousticwavefield to the space-time domain.

In a further embodiment of the present invention, illustrated in FIG. 2,the two receivers (201) are offset (250) in substantially the in-linedirection (225). The in-line (225) or sail direction, as it is oftencalled, represents the direction of travel of the seismic vessel (210).As will occur to those skilled in the art, the direction of travel (225)or in-line direction, is also the direction that the receivers (201) arebeing towed. Therefore, in these embodiments, the offset (250) isparallel with the direction of travel (225) of the seismic vessel (210).Furthermore, in many embodiments, many receivers (201) are positioned onthe seismic streamer (220) and pulled by the seismic vessel (210). Asillustrated in FIG. 2, in another embodiment, the two receivers (201)are substantially at the same depth (205). In some embodiments, at leasta portion of a scattered acoustic wavefield (230) is received at each ofthe receivers (201). As will occur to those skilled in the art, thescattered acoustic wavefield (230) is generated by various methods thatwill occur to those of ordinary still in the art. Such methods include,for example, using air guns, dynamite, and marine vibrators. Thisgenerated acoustic wavefield is refracted and reflected by variousconditions and layers of earth, water, and other materials. Only aportion of the entire scattered acoustic wavefield (230) is received atany given receiver (201). Thus, those of ordinary skill in the art willappreciate that any reference to a received scattered acoustic wavefield(230) is referring to at least a portion of a scattered acousticwavefield (230) generated. The portion of the scattered acousticwavefield (230) which is actually received is dependent upon variousconditions of the environment and equipment used, as will occur to thoseof ordinary skill in the art.

In an even further embodiment, illustrated in FIG. 3, the two receivers(201) are offset (250) in the cross-line direction (325). The cross-linedirection (325) is substantially perpendicular to the direction oftravel (225) of the seismic vessel (210). As will occur to one ofordinary skill in the art, conventional towing methods tow numerousreceivers (201) on a plurality of streamers (220). Therefore, there isgreater coverage in the in-line direction (225) than in the cross-linedirection.

In an even further embodiment of the present invention, transforming(101) the scattered acoustic wavefield (230) to the frequency domainfurther comprises using a Fourier transform. In another embodiment, theFourier transform is dependent upon the number of receivers (201)receiving the scattered acoustic wavefield (230). In an even furtherembodiment, this Fourier transform further comprises:

p ^(sct)(x _(1,q) ^(R) ,x _(2,r) ^(R) ,x ₃ ^(R) |X ^(S) ,s)

wherein:

s=jω=j2πf

p^(sct) comprises the scattered acoustic wavefield in the frequencydomain.

x_(1,q) ^(R) comprises the in-line receiver coordinate.

x_(2,r) ^(R) comprises the cross-line receiver coordinate.

x₃ ^(R) comprises the receiver depth coordinate.

X^(S)=(x₁ ^(S),x₂ ^(S),x₃ ^(S)) comprises the shot position.

s comprises the complex Laplace transform parameter.

jω comprises the Fourier transform parameter.

j comprises the imaginary unit.

f comprises the real frequency.

Of course, in various embodiments, many Fourier transforms such as FastFourier Transforms (FFT), Discrete Fourier Transforms (DFT), anddiscrete versions of the Laplace Transforms will occur to those ofordinary skill in the art. Transforming the scattered acoustic wavefieldto the frequency domain provides many benefits. For example,differentiation with respect to time becomes a simple multiplication inthe frequency domain, and a time convolution becomes a simple product inthe frequency domain.

In a further embodiment, the transforming (105) the scattered acousticwavefield (230) to the spectral domain also comprises using a Fouriertransform. As will occur to those of ordinary skill in the art, thespectral domain results are obtained after a Fourier transform of thefrequency domain results with respect to space. In some embodiments,this Fourier transform is dependent upon the number of receivers (201)receiving the scattered acoustic wavefield (230). In an even furtherembodiment, the Fourier transform further comprises:${P^{sct}\left( {{j\quad s\quad \alpha_{n}},{j\quad s\quad \beta_{m}},\left. x_{3}^{R} \middle| X^{s} \right.,s} \right)} = \quad {\quad {\quad {\Delta \quad x_{1}^{R}\Delta \quad x_{2}^{R}\underset{q = {{{{- 1}/2}N} + 1}}{\overset{{1/2}N}{\quad\sum}}{\sum\limits_{r = {{{{- 1}/2}M} + 1}}^{{1/2}M}{{\exp \left( {{j\quad s\quad \alpha_{n}x_{1,q}^{R}} + {j\quad s\quad \beta_{m}x_{2,r}^{R}}} \right)}{p^{sct}\left( {x_{1,q}^{R},x_{2,r}^{R},\left. x_{3}^{R} \middle| X^{s} \right.,s} \right)}}}}}}$

wherein:${{s\quad \alpha_{n}} = {n\frac{2\pi}{N\quad \Delta \quad x_{1}^{R}}}},{n = {{{{- 1}/2}N} + 1}},\ldots \quad,{{1/2}N}$

and wherein:${{s\quad \beta_{m}} = {m\frac{2\pi}{M\quad \Delta \quad x_{2}^{R}}}},{m = {{{{- 1}/2}M} + 1}},\ldots \quad,{{1/2}M}$

P^(sct) comprises the spectral scattered acoustic wavefield.

Δx₁ ^(R) comprises the in-line receiver sampling distance.

Δx₂ ^(R) comprises the cross-line receiver sampling distance.

q comprises the in-line receiver number.

r comprises the cross-line receiver number.

jsα_(n) comprises the in-line spectral Fourier parameter.

jsβ_(m) comprises the cross-line spectral Fourier parameter.

x_(1,q) ^(R) comprises the in-line receiver coordinate.

x_(2,r) ^(R) comprises the cross-line receiver coordinate.

p^(sct) comprises the scattered acoustic wavefield in the frequencydomain.

x₃ ^(R) comprises the receiver depth coordinate.

X^(S)=(x₁ ^(S),x₂ ^(S),x₃ ^(S)) comprises the shot position.

s comprises the complex Laplace transform parameter.

n comprises the in-line spectral index.

N comprises the total number of in-line receivers.

m comprises the cross-line spectral index.

M comprises the total number of cross-line receivers.

Again, various other methods of transforming a scattered acousticwavefield to the spectral domain such as, for example, Radon transformswill occur to those of ordinary skill in the art. Transforming to thespectral domain provides several benefits. Differentiation with respectto space becomes a simple multiplication in the spectral domain, and aspace convolution becomes a simple product in the spectral domain—toname just a few.

In an even further embodiment of the present invention, deghosting (110)the scattered acoustic wavefield (230) in the spectral domain is alsodependent upon the number of receivers (201) receiving the scatteredacoustic wavefield (230). The advantage to deghost in the spectraldomain is that it consists of a simple division. The deghosting (110)may be performed in both the in-line (225) and the cross-line (325)direction. In an even further embodiment, the deghosting (110) isdependent upon the vertical propagation coefficient. In one embodimentthe vertical propagation coefficient comprises:${s\quad \Gamma_{n,m}^{R}} = {j\sqrt{\left( \frac{2\quad \pi \quad f}{c} \right)^{2} - \left( {s\quad \alpha_{n}} \right)^{2} - \left( {s\quad \beta_{m}} \right)^{2}}}$

sΓ_(n,m) ^(R) comprises the vertical propagation coefficient.

j comprises the imaginary unit.$\left( \frac{2\quad \pi \quad f}{c} \right)^{2}$

 comprises the squared wavenumber.

c comprises the wavespeed in water.

−(sα_(n))² comprises the squared in-line spectral Fourier parameter.

−(Sβ_(m))² comprises the squared cross-line spectral Fourier parameter.

As will also occur to those of ordinary skill, in alternate embodiments,predetermined values and functions of the vertical propagationcoefficient are used.

In another embodiment, the deghosting (110) further comprises applying:${P^{dgh}\left( {{j\quad s\quad \alpha_{n}},{j\quad s\quad \beta_{m}},\left. 0 \middle| X^{s} \right.,s} \right)} = {{H(f)}\frac{P^{sct}\left( {{j\quad s\quad \alpha_{n}},{j\quad s\quad \beta_{m}},\left. x_{3}^{R} \middle| X^{s} \right.,s} \right)}{2\quad {\sinh \left( {s\quad \Gamma_{n,m}^{R}x_{3}^{R}} \right)}}}$

P^(dgh) comprises the spectral deghosted acoustic wavefield at zerodepth.

H comprises the causal frequency-band filter.

f comprises the frequency.

P^(sct) comprises the spectral scattered acoustic wavefield.

jsα_(n) comprises the in-line spectral Fourier parameter.

jsβ_(m) comprises the cross-line spectral Fourier parameter.

sΓ_(n,m) ^(R) comprises the vertical propagation coefficient.

x₃ ^(R) comprises the receiver depth coordinate.

X^(S)=(x₁ ^(S),x₂ ^(S),x₃ ^(S)) comprises the shot position.

Of course in alternate embodiments, other deghosting equations such as,for example, finite difference methods in space, or any other equationthat will occur to those of ordinary skill in the art are applied to thescattered acoustic wavefield (230).

In an even further embodiment, the transforming (115) the substantiallydeghosted transformed acoustic wavefield to the space-time domainfurther comprises an inverse Fourier transform with respect to thereceiver coordinates, followed by an inverse Fourier transform withrespect to the time. In the latter embodiment, the inverse Fouriertransform with respect to time is dependent upon the number of receivers(201) receiving the scattered acoustic wavefield (230). In an evenfurther embodiment, the Fourier transform comprises:

p ^(dgh)(x _(1,q) ,x _(2,r) ^(R),0|X ^(S) ,t)

p^(dgh) comprises the deghosted acoustic wavefield at zero depth.

x_(1,q) ^(R) comprises the in-line receiver coordinate.

x_(2,r) ^(R) comprises the cross-line receiver coordinate.

X^(S)=(x₁ ^(S),x₂ ^(S),x₃ ^(S)) comprises the shot position.

t comprises the time.

Of course, in various embodiments, any other equation or method oftransforming (115) to the space-time domain is used. Such equations andmethods are for example, the inverse Radon transform or any otherequation or method that will occur to those of ordinary skill.

In an even further embodiment of the present invention, illustrated inFIGS. 4, 5, and 6, a method for processing a scattered acousticwavefield (230) received by at least a first set (501) of two receivers(201) and a second set (502) of two receivers is provided. The first set(501) of two receivers (201) is offset (250) at substantially a firstdepth (515) which is vertically offset (520) from at least a second set(502) of two receivers (201) offset (250) at substantially a seconddepth (505). Turning to FIG. 4, the method comprises transforming (401)the scattered acoustic wavefield (230) received at the first depth (515)to the frequency domain. The method further comprises transforming (405)the scattered acoustic wavefield (230) received at the second depth(505) to the frequency domain (405). The method further comprisestransforming (410) the scattered acoustic wavefield (230) received atthe first depth (515) from the frequency domain to the spectral domain.The method further comprises transforming (415) the scattered acousticwavefield (230) received at the second depth (505) from the frequencydomain to the spectral domain. The method also comprises generating(420) a substantially deghosted scattered acoustic wavefield in thespectral domain. The method further comprises transforming (425) thesubstantially deghosted scattered acoustic wavefield to the space-timedomain. In alternate embodiments, the streamer configuration is directlyabove one another or the streamers are triangularly positioned, as willbe discussed below.

As shown in FIG. 5, in another embodiment, the at least a first set(501) of two receivers (201) are offset (250) in substantially thein-line direction (225) relative to one another and the at least asecond set (502) of two receivers (201) are offset (250) insubstantially the in-line direction (225) relative to one another.

In another embodiment, shown in FIG. 6, the at least a first set (501)of two receivers (201) are offset (250) in substantially the cross-linedirection (325) relative to one another and the at least a second set(502) of two receivers (201) are offset (250) in substantially thecross-line direction (325) relative to one another.

In an even further embodiment, transforming (401) the scattered acousticwavefield (230) received at the first depth (515) and the transforming(405) the scattered acoustic wavefield (230) and a second depth (505) tothe frequency domain further comprises using a Fourier transform. In oneembodiment this Fourier transform is dependent upon the number ofreceivers (201) receiving the scattered acoustic wavefield (230). In aneven further embodiment, the Fourier transform further comprises:

p ₁ ^(sct)(x _(1,q) ^(R) ,x _(2,r) ^(R) ,x ₃ ^(R(1)) |X ^(S) ,s) at thefirst depth,

and

p ₂ ^(sct)(x _(1,q) ^(R) ,x _(2,r) ^(R) ,x ₃ ^(R(2)) |X ^(S) ,s) at thesecond depth,

wherein:

s=jω=j2πf

p₁ ^(sct) comprises the scattered acoustic wavefield in the frequencydomain at the first depth.

p₂ ^(sct) comprises the scattered acoustic wavefield in the frequencydomain at the second depth.

x_(1,q) ^(R) comprises the in-line receiver coordinate.

x_(2,r) ^(R) comprises the cross-line receiver coordinate.

x₃ ^(R(1)) comprises the first receiver depth coordinate.

x₃ ^(R(2)) comprises the second receiver depth coordinate.

X^(S)=(x₁ ^(S),x₂ ^(S),x₃ ^(S)) comprises the shot position.

s comprises the complex Laplace transform parameter.

jω comprise the Fourier transform parameter.

j comprises the imaginary unit.

f comprises the real frequency.

In an even further embodiment, the transforming (410) the scatteredacoustic wavefield (230) received at a first depth (515) to the spectraldomain and the transforming (415) the scattered acoustic wavefield (230)received and a second depth (505) to the spectral domain comprises usinga Fourier transform. In some embodiments, the Fourier transform isdependent upon the number of receivers (201) receiving the scatteredacoustic wavefield (230). In another embodiment, the Fourier transformfurther comprises:${P_{1}^{sct}\left( {{j\quad s\quad \alpha_{n}},{j\quad s\quad \beta_{m}},\left. x_{3}^{R{(1)}} \middle| X^{s} \right.,s} \right)} = \quad {\quad {\quad {\Delta \quad x_{1}^{R}\Delta \quad x_{2}^{R}\underset{q = {{{{- 1}/2}N} + 1}}{\overset{{1/2}N}{\quad\sum}}{\sum\limits_{r = {{{{- 1}/2}M} + 1}}^{{1/2}M}{{\exp \left( {{j\quad s\quad \alpha_{n}x_{1,q}^{R}} + {j\quad s\quad \beta_{m}x_{2,r}^{R}}} \right)}{p_{1}^{sct}\left( {x_{1,q}^{R},x_{2,r}^{R},\left. x_{3}^{R{(1)}} \middle| X^{s} \right.,s} \right)}}}}}}$

at the first depth, and${P_{2}^{sct}\left( {{j\quad s\quad \alpha_{n}},{j\quad s\quad \beta_{m}},\left. x_{3}^{R{(2)}} \middle| X^{s} \right.,s} \right)} = \quad {\quad {\quad {\Delta \quad x_{1}^{R}\Delta \quad x_{2}^{R}\underset{q = {{{{- 1}/2}N} + 1}}{\overset{{1/2}N}{\quad\sum}}{\sum\limits_{r = {{{{- 1}/2}M} + 1}}^{{1/2}M}{{\exp \left( {{j\quad s\quad \alpha_{n}x_{1,q}^{R}} + {j\quad s\quad \beta_{m}x_{2,r}^{R}}} \right)}{p_{2}^{sct}\left( {x_{1,q}^{R},x_{2,r}^{R},\left. x_{3}^{R{(2)}} \middle| X^{s} \right.,s} \right)}}}}}}$

at the second depth,

wherein:${{s\quad \alpha_{n}} = {n\frac{2\pi}{N\quad \Delta \quad x_{1}^{R}}}},{n = {{{{- 1}/2}N} + 1}},\ldots \quad,{{1/2}N}$

and wherein:${{s\quad \beta_{m}} = {m\frac{2\pi}{M\quad \Delta \quad x_{2}^{R}}}},{m = {{{{- 1}/2}M} + 1}},\ldots \quad,{{1/2}M}$

P₁ ^(sct) comprises the spectral scattered acoustic wavefield at thefirst depth.

P₂ ^(sct) comprises the spectral scattered acoustic wavefield at thesecond depth.

Δx₁ ^(R) comprises the in-line receiver sampling distance.

Δx₂ ^(R) comprises the cross-line receiver sampling distance.

q comprises the in-line receiver number.

r comprises the cross-line receiver number.

jsα_(n) comprises the in-line spectral Fourier parameter.

jsβ_(m) comprises the cross-line spectral Fourier parameter.

x_(1,q) ^(R) comprises the in-line receiver coordinate.

x_(2,r) ^(R) comprises the cross-line receiver coordinate.

p₁ ^(sct) comprises the scattered acoustic wavefield in the frequencydomain at the first depth.

p₂ ^(sct) comprises the scattered acoustic wavefield in the frequencydomain at the second depth.

x₃ ^(R(1)) comprises the receiver coordinate at the first depth.

x₃ ^(R(2)) comprises the receiver coordinate at the second depth.

X^(S)=(x₁ ^(S),x₂ ^(S),x₃ ^(S)) comprises the shot position.

s comprises the complex Laplace transform parameter.

n comprises the in-line spectral index.

N comprises the total number of in-line receivers.

m comprises the cross-line spectral index.

M comprises the total number of cross-line receivers.

As above, transforming to the spectral domain is desired becausedifferentiation with respect to space becomes a simple multiplication inthe spectral domain, and a space convolution becomes a simple product inthe spectral domain to name only a few benefits.

In an even further embodiment, the generating (420) a deghostedscattered acoustic wavefield in the spectral domain is dependent uponthe number of receivers (201) receiving the scattered acoustic wavefield(230). In some embodiments, generating (420) a deghosted scatteredacoustic wavefield is dependent upon the scattered acoustic wavefield(230) received at a first depth (515) and the scattered acousticwavefield (230) received at second depth (505).

In an even further embodiment, generating (420) further comprisesapplying a filter. In one embodiment this filter comprises:

P ^(dgh) =P ^(dgh)(jsα _(n) ,jsβ _(m),0|X ^(S) ,s)

wherein:$P^{dgh} = {{H(f)}\frac{1}{2}\frac{{\left\lbrack {\sinh \left( {s\quad \Gamma_{n,m}^{R}x_{3}^{R{(1)}}} \right)} \right\rbrack P_{1}^{sct}} + {\left\lbrack {\sinh \left( {s\quad \Gamma_{n,m}^{R}x_{3}^{R{(2)}}} \right)} \right\rbrack P_{2}^{sct}}}{\left| {\sinh \left( {s\quad \Gamma_{n,m}^{R}x_{3}^{R{(1)}}} \right)} \middle| {}_{2}{+ \left| \sinh \left( {s\quad \Gamma_{n,m}^{R}x_{3}^{R{(2)}}} \right) \right.} \right|^{2}}}$

P^(dgh) comprises the spectral deghosted acoustic wavefield at zerodepth.

H comprises the causal frequency-band filter.

f comprises the frequency.

P₁ ^(sct) comprises the spectral scattered acoustic wavefield at thefirst depth.

P₂ ^(sct) comprises the spectral scattered acoustic wavefield at thesecond depth.

jsα_(n) comprises the in-line spectral Fourier parameter.

jsβ_(m) comprises the cross-line spectral Fourier parameter.

sΓ_(n,m) ^(R) comprises the vertical propagation coefficient.

x₃ ^(R(1)) comprises the receiver coordinate at the first depth.

x₃ ^(R(2)) comprises the receiver coordinate at the second depth.

X^(S)=(x₁ ^(S),x₂ ^(S),x₃ ^(S)) comprises the shot position.

In another embodiment, the filter further comprises:

P ^(dgh) =P ^(dgh)(jsα _(n) ,jsβ _(m),0|X ^(S) ,s)

wherein:$P^{dgh} = {{H(f)}\frac{{{\exp \left( {{- s}\quad \Gamma_{n,m}^{R}x_{3}^{R{(1)}}} \right)}P_{2}^{sct}} - {{\exp \left( {{- s}\quad \Gamma_{n,m}^{R}x_{3}^{R{(2)}}} \right)}P_{1}^{sct}}}{2{\sinh \left( {s\quad \Gamma_{n,m}^{R}d} \right)}}}$

wherein:

d=x ₃ ^(R(2)) −x ₃ ^(R(1))

P^(dgh) comprises the spectral deghosted acoustic wavefield at zerodepth.

H comprises the causal frequency-band filter.

f comprises the frequency.

P₁ ^(sct) comprises the spectral scattered acoustic wavefield at thefirst depth.

P₂ ^(sct) comprises the spectral scattered acoustic wavefield at thesecond depth.

jsα_(n) comprises the in-line spectral Fourier parameter.

jsβ_(m) comprises the cross-line spectral Fourier parameter.

sΓ_(n,m) ^(R) comprises the vertical propagation coefficient.

x₃ ^(R(1)) comprises the receiver coordinate at the first depth.

x₃ ^(R(2)) comprises the receiver coordinate at the second depth.

X^(S)=(x₁ ^(S),x₂ ^(S),x₃ ^(S)) comprises the shot position.

d comprises the vertical distance between the first and the second depthof the receivers.

In still a further embodiment, the filter further comprises:$P^{dgh} = {P^{dgh}\left( {{j\quad s\quad \alpha_{n}},{j\quad s\quad \beta_{m}},\left. \frac{x_{3}^{R{(1)}} + x_{3}^{R{(2)}}}{2} \middle| X^{s} \right.,s} \right)}$

wherein:$P^{dgh} = {{H(f)}\frac{{{\exp \left( {s\quad \Gamma_{n,m}^{R}{d/2}} \right)}P_{2}^{sct}} - {{\exp \left( {{- s}\quad \Gamma_{n,m}^{R}{d/2}} \right)}P_{1}^{sct}}}{2{\sinh \left( {s\quad \Gamma_{n,m}^{R}d} \right)}}}$

P^(dgh) comprises the spectral deghosted acoustic wavefield at the depthlevel exactly between the first and the second receiver depths.

H comprises the causal frequency-band filter.

f comprises the frequency.

P₁ ^(sct) comprises the spectral scattered acoustic wavefield at thefirst depth.

P₂ ^(sct) comprises the spectral scattered acoustic wavefield at thesecond depth.

jsα_(n) comprises the in-line spectral Fourier parameter.

jsβ_(m) comprises the cross-line spectral Fourier parameter.

sΓ_(n,m) ^(R) comprises the vertical propagation coefficient.

x₃ ^(R(1)) comprises the receiver coordinate at the first depth.

x₃ ^(R(2)) comprises the receiver coordinate at the second depth.

X^(S)=(x₁ ^(S),x₂ ^(S),x₃ ^(S)) comprises the shot position.

d comprises the vertical distance between the first and the second depthof the receivers.

As above, deghosting in the spectral domain has various benefits, forexample, the deghosting is actualized by simple multiplication anddivision.

In an even further embodiment, transforming (425) the substantiallydeghosted scattered acoustic wavefield to the space-time domain furthercomprises an inverse Fourier transform with respect to the receivercoordinates, followed by an inverse Fourier transform with respect tothe time. In the latter embodiment, the inverse Fourier transform withrespect to time is dependent upon the number of receivers (201)receiving the scattered acoustic wavefield (230). In an even furtherembodiment, the Fourier transform further comprises:

p ^(dgh)(x _(1,q) ^(R) ,x _(2,r) ^(R) ,x ₃ ^(dgh) |X ^(S) ,t)

p^(dgh) comprises the deghosted acoustic wavefield at the depth x₃^(dgh).

x_(1,q) ^(R) comprises the in-line receiver coordinate.

x_(2,r) ^(R) comprises the cross-line receiver coordinate.

x₃ ^(dgh) comprises the appropriate deghosting depth level.

X^(S)=(x₁ ^(S),x₂ ^(S),x₃ ^(S)) comprises the shot position.

t comprises the time.

Turning now to FIG. 7, a method for receiving an acoustic wavefieldbeneath the surface of the water is also provided. In one embodiment,the method comprises receiving at least a portion of an acousticwavefield (230) at a first position (701). The method also comprisesreceiving at least a portion of an acoustic wavefield at a secondposition (702) and receiving at least a portion of an acoustic wavefieldat a third position (703). As shown in FIG. 7, the first position (701),the second position (702), and the third position (703) are triangularlypositioned (720) relative to one another. One of ordinary skill in theart will recognize that in FIG. 7, the positions of reception(701)(702)(703) appear to be at the corners of a triangle (720).Furthermore, the first position (701) is not directly above or below thesecond position (702). The first position (701) is also not directlyabove or below the third position (703). The second position (702) isnot directly above or below the third position (703). As will occur tothose of ordinary skill in the art, receiving is accomplished throughthe use of hydrophones, geophones, accelerometers, or any other receiverthat will occur to those of ordinary skill in the art.

In some embodiments, triangularly positioned (720) further compriseslocating the first position (701), the second position (702) and thethird position (703) on the corners of a triangle when viewed from thein-line direction (225). As will occur to those of ordinary skill in theart, this method for receiving an acoustic wavefield (230) contradictsconventional methods which desire the streamers to be directly above oneanother. However, receivers (201) are mounted on streamers at theselocations (701) (702) (703) on at least three seismic streamers (710)(740) (730). In alternate embodiments, the triangle (720) is anisosceles triangle, and an equilateral triangle, an obtuse triangle, orany other triangle that will occur to one of ordinary skill in the art.

In another embodiment of the present invention, illustrated in FIGS. 9and 10, a method of controlling the quality of seismic data acquisitionsubstantially near the acquisition site is provided. The methodcomprises generating (901) a scattered acoustic wavefield (230). Ascattered acoustic wavefield (230) may be generated (901) by using forexample, a seismic source (1001) such as dynamite, an airgun, a marinevibrator, or any other method of generating a scattered acousticwavefield (230) that will occur to those of ordinary skill in the art.

The method further comprises receiving (905) at least a portion of thescattered acoustic wavefield (230). Seismic sensors such as hydrophones,geophones, accelerometers, and the like may be used to receive at leasta portion of a scattered acoustic wavefield at a given location—wherethe sensor is located. Of course any other method of receiving (905) atleast a portion of a scattered acoustic wavefield (230) such as pressureand/or velocity sensitive devices may also be used. Furthermore, infurther embodiments, receiving (905) includes a computer which isdesigned to accept an acoustic wavefield (230).

The method further comprises substantially deghosting (910) thescattered acoustic wavefield (230) relatively near the acquisition site.Often this substantial deghosting (910) will be during the acquisitionphase itself. For example, the deghosting (910) may be performed on theseismic vessel (210) in marine acquisition situations and near theacquisition site in land acquisition situations. Various methods ofdeghosting are taught herein and other methods of deghosting such asspace-time difference methods and space-frequency methods will occur tothose of ordinary skill in the art. In alternate embodiments, thedeghosting (910) is performed in either the in-line (225) direction orthe cross-line (325) direction. In various embodiments, the deghosting(910) is performed in the time domain, the frequency domain, thespectral domain, the wave number domain, or any other domain which willoccur to those of ordinary skill in the art.

The method further comprises evaluating (915) the quality of thesubstantially deghosted scattered acoustic wavefield. In one embodiment,the quality is compared with predetermined standards that will occur tothose of ordinary skill. In alternate embodiments, the quality issubjectively evaluated by a person (1005) at the acquisition site. Ofcourse, in an even further embodiment, the quality is evaluated (915) bycomputer assistance, or by any other method that will occur to those ofordinary skill in the art. By evaluating (915) the quality of theseismic data, a decision can be made as to whether the data is suitablefor processing. If the data is not suitable for processing, new data maybe acquired before leaving the area. As will occur to those skilled inthe art, what is suitable will vary upon further processing to beperformed and various conditions surrounding the geographic andeconomics of the seismic data acquisition.

In an even further embodiment, the acquisition site is on land. Inanother marine embodiment, the method further comprises generating (901)a scattered acoustic wavefield (230) in the water. In another marineembodiment, the method comprises receiving (905) at least a portion ofthe scattered acoustic wavefield (230) below the surface (260) of thewater (270). In a further embodiment, the method comprises substantiallydeghosting (910) the scattered acoustic wavefield (230) on board aseismic boat (210). By deghosting on board the boat (210) or vessel(210), the quality of the data (1030) can be evaluated before the boat(210) or vessel (210) leaves the acquisition site.

In a further embodiment, a system for processing a scattered acousticwavefield (230) received by at least two receivers (201) offset (250)and located at approximately the same depth (205) is provided. Turningnow to FIG. 11, in one embodiment, the system comprises means fortransforming (1101) the scattered acoustic wavefield (230) to thefrequency domain. In various embodiments, means for transforming (1101)may be a digital computer or analog machine capable of implementing adomain changing formula, a Fourier transformer, a calculator, an analogmachine, or a pen, pencil or other utensil used by one of ordinary skillin the art to change the domain of the scattered acoustic wavefield(230). Of course, in alternate embodiments, means for transforming(1101) comprises Fast Fourier Transformsers (FFT), Discrete FourierTransformers (DFT), and means for performing discrete versions of theLaplace Transforms or any other means that would occur to those ofordinary skill in the art.

The system further comprises means for transforming (1110) the scatteredacoustic wavefield (230) from the frequency domain to the spectraldomain. In various embodiments, means for transforming (1110) is adigital computer or analog machine capable of implementing a domainchanging formula, or a Fourier transformer, a calculator, an analogmachine or a pen, pencil or other utensil used by one of ordinary skillin the art to change the domain of the scattered acoustic wavefield(230).

The system further comprises means for deghosting (1115) the scatteredacoustic wavefield (230) in the spectral domain. In various embodiments,means for deghosting (1115) is a digital computer, analog machine, orutensil which can apply a deghosting algorithm, equation, filter orprocess. Of course in further embodiments, means for deghosting is anyother means that will occur to those of ordinary skill in the art. Ofcourse, in alternate embodiments the means for deghosting is providedfor deghosting the scattered acoustic wavefield in the frequency, time,wave number or any other domain which will occur to those of ordinaryskill in the art.

The system further comprises means for transforming (1120) thesubstantially deghosted transformed acoustic wavefield (230) to thespace-time domain. Of course in various embodiments, means fortransforming (1120) is a digital computer or analog machine capable ofapplying a domain changing formula, algorithm, or process, or any othermeans that will occur to those of ordinary skill in the art.

In a further embodiment, a system for processing a scattered acousticwavefield (230) received by at least a first set (501) of two receivers(201) and a second set (502) of two receivers (201) is provided. Thefirst set (501) of two receivers (201) are offset (250) at substantiallya first depth (515) which is vertically offset (520) from at least thesecond set (502) of two receivers (201) offset (250) at substantially asecond depth (505).

Referring to FIG. 12, the system comprises a means for transforming(1201) the scattered acoustic wavefield (230) received at the firstdepth (515) to the frequency domain and a means for transforming (1205)the scattered acoustic wavefield (230) received at the second depth(505) to the frequency domain. In various embodiments, this means fortransforming (1201)(1205) further comprises a digital computer or analogmachine capable of transforming a domain, or implementing a Fouriertransform, or any other means that will occur to those of ordinary skillin the art. As will occur to those of ordinary skill in the art, themeans for transforming (1205) at the first depth (515) and the seconddepth (505) may be the same in some embodiments and different in others.

The system further comprises means for transforming (1210) the scatteredacoustic wavefield (230) received at the first depth (515) from thefrequency domain to the spectral domain and a means for transforming(1215) the scattered acoustic wavefield (230) received at the seconddepth (505) to the spectral domain. In various embodiments, this meansfor transforming (1210) further comprises a digital computer or analogmachine capable of transforming a domain, or implementing a Fouriertransform, or any other means that will occur to those of ordinary skillin the art. As will occur to those of ordinary skill in the art, themeans for transforming (1210)(1215) at the first depth (515) and thesecond depth (505) may be the same in some embodiments and different inothers.

The system further comprises means for generating (1220) a substantiallydeghosted scattered acoustic wavefield in the spectral domain. Invarious embodiments, this means for generating (1220) a substantiallydeghosted scattered acoustic wavefield further comprises a digitalcomputer or analog machine capable of performing a deghosting algorithm,process or method, a filter, or any other means that will occur to thoseof ordinary skill in the art. Of course, in alternate embodiments themeans for generating a substantially deghosted scattered acousticwavefield is a means for generating in the frequency, time, wave numberor any other domain which will occur to those of ordinary skill in theart.

The system further comprises means for transforming (1225) thesubstantially deghosted scattered acoustic wavefield to the space-timedomain. In various embodiments, this means for transforming (1225)further comprises a digital computer or analog machine capable ofapplying a domain changing formula, a Fourier transformer, or any othermeans that will occur to those of ordinary skill in the art.

In another embodiment of the present invention, a system for receivingacoustic wavefield beneath the surface of the water is provided.Referring to FIG. 13 and FIG. 7, the system comprises means forreceiving (1305)(1310)(1315) at least a portion of an acoustic wavefieldat a first position (701), a second position (702), and a third position(713). In various embodiments, means for receiving seismic receivers(201) are positioned to receive the acoustic wavefield at a givenlocation (701)(702)(713) on seismic streamers (710)(740)(730). Variousreceivers are geophones, hydrophones, accelerometers, pressure and/orvelocity sensitive devices or any other means that will occur to thoseof ordinary skill in the art.

In an even further embodiment, the first position (701), the secondposition (702), and the third position (713) are triangularly positionedrelative to one another. In another embodiment, triangularly positionedfurther comprises means for locating the means for receiving (1305) atthe first position (701), the means for locating the means for receiving(1310) at the second position (702), and the means for locating themeans for receiving (1315) at the third position (713) on the corners ofa triangle when viewed from the in-line direction (225). In variousembodiments, the triangle (720) is an isosceles triangle, an equilateraltriangle, or any other triangle that will occur to those of ordinaryskill in the art. In various embodiments, the means for locating arestreamers with receivers secured to them at the first (701) second (702)and third (703) locations. In even further embodiments, means forlocating (1305), (1310), (1315) are structural means capable of securingstreamers or receivers in relative position to one another.

A system of controlling the quality of seismic data acquisitionsubstantially near the acquisition site is provided. The system isillustrated in block diagram form in FIG. 14. The system comprises ameans for generating (1401) a scattered acoustic wavefield (230). Inalternate embodiments, this means for generating (1401) a scatteredacoustic wavefield (230) is an air gun, dynamite, a marine vibrator, orany other means that will occur to those of ordinary skill in the art.In various embodiments, these means are employed below or above thesurface of water, on land or any other location that will occur to thoseof ordinary skill in the art.

The system further comprises means for receiving (1405) at least aportion of the scattered acoustic wavefield (230). In variousembodiments, means for receiving (1405) a portion of a scatteredacoustic wavefield (230) are seismic receivers such as hydrophones,geophones, accelerometers, pressure and/or velocity sensitive devices orany other means that will occur to those of ordinary skill in the art.In various embodiments, these receivers are employed below or above thesurface of water, on land or any other location that will occur to thoseof ordinary skill in the art. In even further various embodiments,receivers are located at various depths, the same depth, on a singlestreamer, or on multiple streamers. In even further embodiments, meansfor receiving (1405) is a digital computer or analog machine which canaccept a scattered acoustic wavefield for processing. In variousembodiments, such computers and analog machines or any other means thatwill occur to those of ordinary skill in the art.

The system further comprises a means for substantially deghosting (1410)the scattered acoustic wavefield (230) relatively near the acquisitionsite. In some embodiments, such means (1410) is a digital computer oranalog machine capable of applying a deghosting equation algorithm orprocess, or any other means that will occur to those of ordinary skillin the art.

The system further comprises a means for evaluating (1415) the qualityof the substantially deghosted scattered acoustic wavefield. In variousembodiments, means for evaluating (1415) is a digital computer or analogmachine capable of comparing various attributes of the data acquiredwith predetermined standards. In even further embodiments, the means forevaluating (1415) is a digital computer, or analog machine, or any othermeans that will occur to those of ordinary skill in the art.

In an even further embodiment, an apparatus for processing a scatteredacoustic wavefield (230) received by at least two receivers (201) whichare offset (250) and located at approximately the same depth (205) isprovided. The apparatus comprises a frequency domain transformer (1501).In various embodiments, the frequency domain transformer (1501)comprises a digital computer or analog machine capable of changing thedomain of a scattered acoustic wavefield (230), a digital computer oranalog machine capable of applying a Fourier transformer, or any otherdomain transformer that will occur to those of ordinary skill in theart.

The apparatus further comprises a spectral domain transformer (1505). Invarious embodiments, the spectral domain transformer (1505) comprises adigital computer or analog machine capable of changing the domain of ascattered acoustic wavefield (230), a digital computer or analog machinecapable of applying a Fourier transformer or any other domaintransformer that will occur to those of ordinary skill in the art.

The apparatus further comprises a deghoster (1510). In variousembodiments, the deghoster (1510) is a digital computer or analogmachine capable of applying a deghosting equation, filter, algorithm, ormethod, or any other deghoster that will occur to those of ordinaryskill in the art.

The apparatus further comprises a space-time domain transformer (1515).In various embodiments, the space-time domain transformer (1515)comprises a digital computer or analog machine capable of changing thedomain of a scattered acoustic wavefield (230). In even furtherembodiments, the space-time domain transformer (1515) further comprisesa digital computer or analog machine capable of applying a Fouriertransform, or any other domain changing equation, algorithm, filter,method, or any other domain transformer that will occur to those ofordinary skill in the art.

In an even further embodiment, the apparatus is capable of being used onboard a seismic vessel (210). In an even further embodiment, anapparatus for processing a scattered acoustic wavefield (230) receivedby at least a first set (501) of two receivers and a second set (502) oftwo receivers (201). The first set of two (501) receivers (201) isoffset (250) at substantially a first depth (515) which is verticallyoffset (520) from at least a second set (502) of two receivers (201)offset (250) at substantially a second depth (505) is provided. Asillustrated in block diagram form, in FIG. 16, the apparatus comprises afirst depth frequency domain transformer (1601). In various embodiments,the first depth (515) frequency domain transformer (1601) comprises adigital computer or analog machine capable of changing the domain, adigital or analog machine capable of applying a Fourier transform, orany other transformer that will occur to those of ordinary skill in theart.

The apparatus further comprises a second depth (505) frequency domaintransformer (1605). In various embodiments, the second depth (505)frequency domain transformer (1605) comprises a digital computer oranalog machine capable of changing the domain, a digital or analogmachine capable of applying a Fourier transform or any other transformerthat will occur to those of ordinary skill in the art.

The apparatus further comprises a first depth (515) spectral domaintransformer (1610). In various embodiments, the first depth (515)spectral domain transformer (1610) comprises a digital computer oranalog machine capable of changing the domain, a digital or analogmachine capable of applying a Fourier transform or any other transformerthat will occur to those of ordinary skill in the art.

The apparatus further comprises a second depth (505) spectral domaintransformer (1615). In various embodiments, the second depth (505)spectral domain transformer (1615) comprises a digital computer oranalog machine capable of changing the domain, a digital or analogmachine capable of applying a Fourier transform or any other transformerthat will occur to those of ordinary skill in the art.

The apparatus further comprises a deghoster (1620). In variousembodiments, the deghoster (1620) comprises a digital computer or analogmachine capable of applying a deghosting equation, filter, or method, orany other deghoster that will occur to those of ordinary skill in theart.

The apparatus further comprises a space-time domain transformer (1625).In various embodiments, the space-time domain transformer (1625)comprises a digital computer or analog machine capable of changing thedomain, a digital or analog machine capable of applying a Fouriertransform or any other transformer that will occur to those of ordinaryskill in the art.

In an even further embodiment of the present invention, a streamerconfiguration is provided. As illustrated in FIGS. 7 and 8, the streamerconfiguration comprises a first seismic streamer (710), a second seismicstreamer (740) and a third seismic streamer (730). Seismic streamers areavailable and widely known to those of ordinary skill in the art.

In the present configuration, the first seismic streamer (710), thesecond seismic streamer (740), and the third seismic streamer (730) areessentially triangularly positioned relative to one another. In oneembodiment, triangularly positioned further comprises having the firstseismic streamer (710), the second seismic streamer (740), and the thirdseismic streamer (730) positioned at a corner of a triangle when viewedfrom the in-line direction (225). Furthermore, the first streamer (710)is not directly above or below the second (740) or third (730) streamer.Even further, the second streamer (740) is not above or below the thirdstreamer (730). The seismic streamers (710) (740) (730) support seismicreceivers (701) (702) (703) which receive at least a portion of anacoustic wavefield in this configuration.

In a further embodiment, triangularly positioned further comprisespositioned at the corner of an equilateral triangle, at corner of anisosceles triangle, or any other triangle that will occur to those ofordinary skill in the art.

In an even further embodiment, an apparatus for controlling the qualityof seismic data acquisition at the acquisition site is provided. Theapparatus is illustrated in block diagram form in FIG. 18. The apparatuscomprises a scattered acoustic wavefield (230) generator (1701). Invarious embodiments, this scattered acoustic wavefield (230) generator(1701) is a seismic source such as an airgun, dynamite, marine vibrator,or any other scattered acoustic wavefield generator.

The apparatus further comprises a scattered acoustic wavefield (230)receiver (1705). In various embodiments, the scattered acousticwavefield (230) receiver (1705) is a digital computer which receiveseither a portion or the full scattered acoustic wavefield (230), or anyother wavefield receiver that will occur to those of ordinary skill inthe art. In alternate embodiments, the scattered acoustic wavefieldreceiver (1705) is a hydrophone, geophone, accelerometer, pressuretransducer, velocity transducer, or any other receiver that will occurto those of ordinary skill in the art.

The apparatus further comprises a deghoster (1710). In variousembodiments, the deghoster (1710) comprises a digital computer or analogmachine capable of deghosting, or any other deghoster that will occur tothose of ordinary skill in the art.

The apparatus further comprises a quality evaluator (1715). In variousembodiments, a quality evaluator (1715) is a digital computer or analogmachine capable of evaluating or comparing seismic data, or any otherquality evaluator that will occur to those of ordinary skill in the art.

In a further embodiment, the apparatus is designed to be located andused near a land acquisition site. In alternate embodiments, theapparatus is relatively near the shot location or the receiver location.In an even further embodiment, the acquisition site is a marineacquisition site. In marine embodiments, the apparatus may be primarilylocated onboard a seismic vessel (210). In doing so, the apparatus willevaluate (1715) the quality of the seismic data while the vessel (210)still has the opportunity to acquire more suitable marine data from thesame area.

As will occur to those of ordinary skill in the art, the above describedembodiments are examples of embodiments of the present invention. Theseexample embodiments are merely illustrative, and in no way exhaustive ofthe scope of the present invention.

We claim:
 1. A method for receiving acoustic wavefield beneath thesurface of the water, the method comprising: receiving at least aportion of an acoustic wavefield at a first position; receiving at leasta portion of an acoustic wavefield at a second position; receiving atleast a portion of an acoustic wavefield at a third position, whereinthe first position, the second position, and the third position aretriangularly positioned relative to one another and wherein the firstposition is not directly above or below the second position and whereinthe first position is not directly above or below the third position andwherein the second position is not directly above or below the thirdposition; transforming the received portions of the acoustic wavefieldfrom the first, the second and the third positions from the space-timedomain to the spatial frequency domain; deghosting the transformedacoustic wavefield; and transforming the deghosted wavefield back to thespace time domain.
 2. The method of claim 1, wherein triangularlypositioned further comprises locating the first position, the secondposition and the third position at the corners of a triangle when viewedfrom the in-line direction.
 3. The method of claim 2, wherein thetriangle is an isosceles triangle.
 4. The method of claim 2 wherein thetriangle is an equilateral triangle.
 5. A system for receiving acousticwavefield beneath the surface of the water, the system comprising: meansfor receiving at least a portion of an acoustic wavefield at a firstposition; means for receiving at least a portion of an acousticwavefield at a second position; means for receiving at least a portionof an acoustic wavefield at a third position, wherein the firstposition, the second position, and the third position are triangularlypositioned relative to one another and wherein the first position is notdirectly above or below the second position and wherein the firstposition is not directly above or below the third position and whereinthe second position is not directly above or below the third position;means for transforming the received portions of the acoustic wavefieldfrom the first, the second and the third positions from the space-timedomain to the spatial frequency domain; means for deghosting thetransformed acoustic wavefield; and means for transforming the deghostedwavefield back to the space time domain.
 6. The system of claim 5,wherein triangularly positioned further comprises locating the firstposition, the second position and the third position at the corners of atriangle when viewed from the in-line direction.
 7. The system of claim5, wherein the triangle is an isosceles triangle.
 8. The system of claim5 wherein the triangle is an equilateral triangle.